1. Field of the Invention
This invention relates to a detergent composition which possesses excellent resistance to hard water, in which the amount of sodium tripolyphosphate employed as a builder can be greatly reduced or sodium tripolyphosphate can be entirely omitted, and which possesses an excellent rinsing property after washing.
2. Description of the Prior Art
Although the demand for sodium tripolyphosphate as a builder component in detergents has been increasing, various limitations have been imposed on the use of this builder because of the wide-spread shortage of phosphate rock, its high price and the like. Further, it is known that phosphate components contained in discharged washing solutions cause eutrophication and pollution in rivers and lakes. Accordingly, in the detergent art, there have been serious problems of how to reduce the amount of sodium tripolyphosphate and how to utilize it more efficiently in detergents.
Various attempts have heretofore been made to solve these problems, and these known attempts are generally divided in two types; one type is directed to a method in which another builder is used as a substitute for sodium tripolyphosphate and the other type is directed to a method in which a surface active agent possessing excellent resistance to hard water is used as the effective detergent component. In the former method, however, there has not been discovered any practical builder that can be used instead of sodium tripolyphosphate and that will provide satisfactorily good results with respect to washing ability, cost and other economic factors, safety and the like. In connection with the latter method, the use of hard water-resistant polyoxyethylene alkyl ether sulfates (hereinafter referred to simply as "ether sulfates" or "ES"), which are salts of sulfuric acid esters of adducts of 3 to 5 moles of ethylene oxide to higher alcohols having 12 to 18 carbon atoms in the alkyl group, has been proposed and practiced. These ether sulfates, which have been effectively used for detergents, have a good resistance to hard water, but they have a foaming characteristic such that foaming increases with an increase of water hardness at low concentrations. This characteristic makes it difficult to remove foam during the rinsing step after washing. In fact, in the case of ether sulfate-containing detergents for clothing, tableware, hair, furniture or the like, foams do not disappear smoothly and sufficiently during the rinsing or finishing step. This defect in rinseability decreases the commercial value of detergent products. Accordingly, if this defect can be ameliorated, it will be possible to provide a phosphate-free or low phosphate detergent having a high commercial value and which can be easily used by consumers with saving of rinsing water.